In the large intestine, the sub-mucosal solitary lymphoid nodules (SLN) was scattered throughout the colon and rectum in all the experimental animals under study. The solitary lymphoid nodules of caecum were apparently visible grossly from the outside as a round dark area (Fig 1a). However, few numbers of solitary lymphoid nodules was observed towards the proximal colon as was reported earlier reported by Dev
Choudhury et al., (2017) in pig and
Gautam et al., (2013) in goat.
The solitary lymphoid nodules were in the form of minute round tubercles with small depression (Fig 1b) at the centre. This is in agreement with the findings of
Morfitt and Pohlenz (1989).
Grossly two different types of solitary lymphatic nodules were observed
viz. scrotiform and faviform .The scrotiform nodule had a small pore on the dome and the faviform with no central pore (Fig 1c). However,
Zhaxi et al., (2014) reported that there were three types of PPs in large intestine in Bactrian Camels
viz. scrotiform, faviform and complete cup-shaped, but in present study it was recorded only scrotiform and faviform lymphatic nodule.
Morfit and Pohlenz (1989) reported that an average of 1,231 number of LGC was present in colon of aged pigs and
Gautam et al., (2013) reported that an average of 68.17±3.15 and 17.33±4.11 number of SNL was recorded in colon and rectum respectively in goat with a total number of SLNs was 85.50±4.47. However, in the present findings it was observed that the concentration of the solitary lymphoid nodule was maximum in the spiral loop of ascending colon, the number decreased towards the distal loop of the ascending colon, descending colon and rectum respectively (Fig 1d). The average solitary lymphoid nodules counted in the large intestine were 427, out of which 403 was in colon and 24 in rectum of weaned piglets. Again, in the terminal part of rectum patches of solitary lymphatic nodules of more than 100 numbers were observed.
In the large intestinal lymphatic circulation, different lymph nodes were involved in the abdominal viscera, abdominal wall and pelvic wall
viz. the anorectal, caudal mesenteric, sacral lumber lumbar aortic, renal and colic lymph nodes (Fig 2a and 2c).
The lymphatic draining tract to the colic lymph nodes was recorded (Fig 2a) by injecting 100 µl of 1% methylene blue in different site of colon and then stained colic lymph nodes were re-injected to map the drainage to the next draining lymph node to trace the lymphatic tract to record the colic trunk . The colic trunk continued as visceral trunk and finally emptied in the cisterna chyli (Fig 2c). Again, it was found that the celiac trunk carried lymph from the cranial part of abdominal viscera and joined the jejunal trunk. The colic trunk then joined the common trunk to form visceral trunk (Fig 2d). However,
Saar and Getty (2012) reported that the colic trunk and jejunal trunk joined to form intestinal trunk in pig and then only the celiac trunk joined to the common intestinal trunk to form visceral trunk in pig.
It was observed that the injected dye from the site of injection reached the anorectal lymph node, from which it reached the caudal mesenteric lymph nodes and then it reached the renal and middle colic lymph node. The left and right lumber trunks joined to form the cysternachyli which appeared as a dilated sac adjacent to renal artery and vein (Fig 2b) and dorsal to aorta from where the lymph was drained out to the caudal vena cava through thoracic duct (Fig 2c). This was in contrary to the findings of
Gomercic et al., (2010) who reported that the cisterna chyli was present at the level of third lumbar vertebra under crura of diaphragm at the origin of renal artery and cranially covered the dorsal surface of aorta in Yorkshire pig.
